title: Mapping of the immunodominant regions of shrimp tropomyosin Pan b 1 by human IgE-binding and IgE receptor crosslinking studies.
abstract: BACKGROUND
  Epitope mapping of an allergen is generally done by IgE-binding assays with short synthetic peptides, but this provides little information about which domains are responsible for IgE receptor crosslinking on effector cells. Our aim was to map the immunodominant regions of shrimp tropomyosin by both IgE-binding and IgE-receptor crosslinking studies.
  
  
  METHODS
  Five overlapping fragments covering Pandalus borealis tropomyosin were cloned, expressed in Escherichia coli and characterized by circular dichroism spectroscopy, native PAGE and bis(sulfosuccinimidyl) suberate-crosslinking. IgE binding was detected by Western blot, indirect ELISA and inhibition ELISA, and IgE receptor crosslinking was investigated by basophil activation test and skin prick test with Norwegian shrimp allergic adults.
  
  
  RESULTS
  The N- and C-terminal fragments of tropomyosin showed the highest amount of secondary structure. Western blot studies showed preferential binding to the terminal fragments, while indirect and inhibition ELISA studies showed binding to all fragments, but with individual variations. Basophil CD63 expression was upregulated by all fragments at high concentrations (1 µg/ml) and showed individual variations comparable to ELISA results. A mixture of the fragments with equal molar ratios induced comparably strong CD63 activation as for tropomyosin. Skin prick test studies showed positive responses to the terminal and middle fragments and increased responses to the fragment mixture compared to whole tropomyosin.
  
  
  CONCLUSIONS
  The terminal and middle fragments of tropomyosin had the highest IgE reactivity, but overall no clear immunodominant region was observed in this study. These results correlated well with previous studies with short peptides. Dividing shrimp tropomyosin into five fragments did not reduce the allergenicity of the protein.
authors.affiliation: Norwegian Veterinary Institute, Oslo, Norway.
authors.forename: Heidi R
authors.initials: HR
authors.lastname: Myrset
authors.forename: Christiane K
authors.initials: CK
authors.lastname: Fæste
authors.forename: Per E
authors.initials: PE
authors.lastname: Kristiansen
authors.forename: Maaike M B W
authors.initials: MM
authors.lastname: Dooper
mesh_terms: D000328:Adult; D000485:Allergens / Q000235:genetics* / Q000276:immunology; D000595:Amino Acid Sequence; D000818:Animals; D060829:Arthropod Proteins / Q000235:genetics* / Q000276:immunology; D002874:Chromosome Mapping; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D016056:Immunodominant Epitopes / Q000235:genetics*; D007073:Immunoglobulin E / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D033542:Pandalidae / Q000235:genetics / Q000276:immunology; D011485:Protein Binding; D017455:Receptors, IgE / Q000378:metabolism*; D016415:Sequence Alignment; D060149:Tetraspanin 30 / Q000276:immunology
chemical_list: D000485:Allergens; D060829:Arthropod Proteins; D016056:Immunodominant Epitopes; C579817:Pan b 1 allergen, Pandalus borealis; D017455:Receptors, IgE; D060149:Tetraspanin 30; D007073:Immunoglobulin E